Asymmetric dendrimers

ABSTRACT

Asymmetric light-emitting dendrimers having the formulae: (a) CORE−[DENDRITE 1 ] n [DENDRITE 2 ] m  and (b) CORE−[DENDRITE] n  are disclosed.

This is the U.S. national phase of International Application No.PCT/GB02/00765 filed Feb. 20, 2002, the entire disclosure of which isincorporated herein by reference.

Light-emitting materials fall into three classes, namely molecular,polymeric, and dendritic. Dendritic materials have several advantagesover molecular and polymeric materials including: a) the electronicproperties can be changed without altering the processing properties; b)a greater variety of chromophores can be used as the dendriticarchitecture can stop π-π stacking of the chromophores; c) theefficiency of light-emitting diodes can be controlled by the dendrimergeneration i.e. the number of sets of branching points within a dendron(also called dendrite); and d) the dendrimer architecture makes theformation of blends with other dendrimers, polymers and molecularmaterials simple. Dendrimers consist of dendrons or dendritic structuresterminating in surface groups and a core (see FIG. 1). Dendrons have atleast one, and preferably more than one, branching point. The branchingpoints are atoms or groups to which at least two linkers or branches areattached. The nature of the branching points and the links between thebranching points can be varied. A branching group can be directlyconnected to the next branching group (e.g. aryl-aryl), or there can belinking groups in between (e.g. aryl-vinyl-aryl). There are at leastthree attachments in total to a branching group, but only two are neededto a linker group. These can be illustrated as follows:

As used herein, the term acetylenyl refers to acetylenyl groups that aredi-valent, vinyl refers to vinyl groups that are di- or tri-valent andaryl refers to aryl groups that are di-, tri- or multivalent.

There have been a number of classes of light-emitting dendrimersreported with the main differences observed in the dendron architecture.The first report of a light-emitting dendrimer had a fluorescent coreand phenylacetylene based dendrons. More recently a superior system hasbeen reported where the dendrimers are again comprised of a fluorescentcore but the dendrons contain stilbene moieties. Dendrimers based onthis latter architecture have been shown to have the advantagesdescribed above over molecular and polymeric materials. Some simpledendrimers that contain biphenyl based dendrons have also beendescribed. Finally, there have been a few reports of dendrimers thatcontain luminescent chromophores but where the dendrons containnon-conjugated branching points. These latter materials have thepotential disadvantage that much of it is comprised of electricallyinsulating groups. The dendrimer types that are likely to have thegreatest promise are those that contain mostly conjugated dendrons.These include those described in WO99/21935; these are compounds havingthe formula:CORE−[DENDRITE]_(n)in which CORE represents an atom or group, n represents an integer of atleast 1 and DENDRITE, which may the same or different if n is greaterthan 1, represents an inherently at least partly conjugated dendriticstructure comprising aryl and/or heteroaryl groups and alkenyl groupsconnected to each other via a carbon atom of an alkenyl group to a ringcarbon atom of an aryl or heteroaryl group, CORE terminating in thefirst single bond which is connected to a ring carbon atom of an(hetero)aryl group to which more than one at least partly conjugateddendritic branch is attached (i.e. a branching point), said ring carbonatom forming part of DENDRITE, the CORE and/or DENDRITE beingluminescent.

In inherently at least partially conjugated dendrons suitable branchinggroups include aryl and heteroaryl where the definition of (hetero)arylincludes aromatic fused ring systems such as naphthalene and fluorene.Suitable linking groups between the branching groups include(hetero)aryl as well as vinyl and acetylenyl groups. In a conjugatedsystem the linking groups are attached to the branching groups by an sp²or sp hybridized carbon atom. Hence suitable links between branchinggroups for at least partially conjugated dendrons include aryl-aryl,aryl-vinyl-aryl, aryl-acetylenyl-aryl, and aryl-aryl′-aryl (where aryl′may be different from aryl). It is also possible for there to be morethan one linking group between branching points so combinations such asaryl-vinyl-acetylenyl-aryl, aryl-aryl′-vinyl-aryl oraryl-aryl′-acetylenyl-aryl are also suitable.

Thus in inherently at least partially conjugated dendrimers the coreterminates at the single bond to the first branching group, i.e. a bondto the ring carbon (sp² carbon) of a (hetero)aryl branching group, thering carbon forming part of the dendron. However, it has now beenappreciated, according to the present invention, that having the samelinking group between the branching points in the dendrons in thedendrimer is not necessarily advantageous. For example, anaryl-vinyl-aryl link may be advantageous for hole transport in an LED(light emitting diode) but for electron transport an aryl-aryl′-aryllinkage such as in a phenyl-oxadiazole-phenyl dendron could havesuperior, properties. Accordingly the present invention provides (a) alight emitting dendrimer having the formula:CORE−[DENDRITE¹]_(n)[DENDRITE²]_(m)in which CORE represents an atom or group, n and m, which may be thesame or different, each represent an integer of at least 1, eachDENDRITE¹, which may be the same or different when n is greater than 1,and each DENDRITE², which may be the same or different when m is greaterthan 1, represent dendritic structures, at least one of said structuresbeing fully conjugated and comprising aryl and/or heteroaryl groups and,-optionally, vinyl and/or acetylenyl groups, connected via sp² or sphybridized carbon atoms of said (hetero) aryl, vinyl and acetylenylgroups, and at least one branching point and/or link between branchingpoints in DENDRITE¹ being different from those in DENDRITE², COREterminating in the single bond which is connected to a sp² hybridized(ring) carbon atom of the first (hetero)aryl group to which more thanone conjugated dendritic branch is attached, said ring carbon atomforming part of said fully conjugated DENDRITE¹ or DENDRITE² and COREterminating at the single bond to the first branching point for theother of said DENDRITE¹ or DENDRITE², at least one of the CORE,DENDRITE¹ and DENDRITE² being luminescent, as well as (b) a lightemitting dendrimer having the formula:CORE−[DENDRITE]_(n)in which CORE represents an atom or group, n represents an integer of atleast 1, each DENDRITE, which may be the same or different, representsan inherently at least partially conjugated dendritic molecularstructure which comprises aryl and/or heteroaryl and, optionally, vinyland/or acetylenyl groups connected via sp² or sp hybridized carbon atomsof said (hetero) aryl, vinyl and acetylenyl groups, and wherein thelinks between at least one pair of adjacent branching points in saidDENDRITE are different such that if two links are to be regarded asdifferent then one said link must comprise at least one aryl,heteroaryl, vinyl or acetylenyl group which is not present in the otherof the said two links, CORE terminating in the single bond which isconnected to a sp² hybridized (ring) carbon atom of the first(hetero)aryl group to which more than one dendritic branch is attached,said ring carbon atom forming part of said DENDRITE, the CORE and/orDENDRITE being luminescent. In a preferred embodiment n is greaterthan 1. Thus the present invention provides, inter alia, dendrimers ofTypes 1 to 4 as shown in FIG. 2.

Thus in Type 1 there are aryl-aryl or, more generally,aryl-(aryl′)_(n)-aryl, wherein aryl includes heteroaryl and aryl′ is thesame as- or different from aryl and a is an integer from 0 to 3, andaryl-vinyl-aryl linkages (or, more generally,aryl-(vinyl)_(x)-[aryl′_(v)-(vinyl)_(y]) _(z)-aryl where x is an integerfrom 1 to 3, preferably 1 or 2, y is an integer from 0 to 3, preferably0, or 2, v and z are independently from 0 to 3 (where the aryl groupsare branching points), in Type 2 aryl-(aryl′)_(a)-aryl andaryl-acetylenyl-aryl linkages (or, more generally,aryl-(acetylenyl)_(d)-[(aryl′)_(e)-(acetylenyl)_(f)]_(g)-aryl where d isan integer from 1 to 3, preferably 1 or 2, f is an integer from 0 to 3,preferably 0, or 2, and e and g a independently 0 to 3), in Type 3aryl-vinyl-aryl and aryl-acetylenyl-aryl linkages (or their more generalvariants) and in Type 4 there are dendrons containing more than one typeof link in each dendron, i.e. aryl-aryl and either aryl-vinyl-aryl oraryl-acetylenyl-aryl (or their more general variants). It is to beunderstood that references to aryl (and aryl′) include heteroaryl andfused aromatic ring systems. Thus the dendrimers contain two or more ofthe following types of linkages between branching points within thedendrites: aryl-aryl, aryl-vinyl-aryl, aryl-acetylenyl-aryl andaryl-vinyl-acetylenyl-aryl. In the last three cases the number of vinyland acetylenyl linkages can be 1 or more and in Type 4 the number andorder of the different units, in this case vinyl and acetylenyl units,can be varied. In addition, one dendron can contain more than one typeof link between the branch points. For example, a single dendron maycontain a mixture of aryl-aryl links and aryl-vinyl-aryl links. It is tobe appreciated that although in these units aryl acts as the branchingpoints, aryl can also be a linking group.

It will be appreciated that in Types 1 to 3 DENDRITE¹ differs fromDENDRITE² by having different branching points and/or different links(because differences in surface groups and/or generation, although theycan be present, are regarded as insignificant for the purposes ofdeciding whether or not the dendritic structures are “different”); inthis regard the branching points and/or links of one of DENDRITE¹ andDENDRITE² are regarded as different from the branching points and/orlinks of the other of DENDRITE¹ and DENDRITE² if the aryl group orgroups in the first one are not all the same as the group or groups ofthe second one. Thus a dendrite with a phenyl-phenyl structure isregarded as different from a dendrite with a phenyl-pyridyl structure.Preferably if DENDRITE¹ differs from DENDRITE² merely in a differentlink then, for two links to be regarded as different one said link mustcomprise at least one aryl, heteroaryl, vinyl or acetylenyl group whichis not present in the other of said two links. Of course suchdifferences can also be present in Type 4 dendrimers. Indeed for Type 4dendrimers a difference merely in the number of vinyl or acetylenylgroups as links should not be regarded as a difference.

In this context, conjugated dendrons (dendrites) indicate that they aremade up of alternating double and single bonds, apart from the surfacegroups. However this does not mean that the π system is fullydelocalised. The delocalisation of the π system is dependent on theregiochemistry of the attachments.

The dendrimer may have more than one luminescent moiety and the energyresulting from electrical or optical excitation may be transferred toone of them for light emission. In a preferred embodiment the dendrimerincorporates at least two inherently at least partially-conjugatedluminescent moieties which moieties may or may not be conjugated witheach other, wherein the dendron includes at least one of the saidluminescent moieties. Preferably the luminescent moiety or moietiesfurther from the core of the dendrimer generally have a larger HOMO-LUMOenergy gap than the, luminescent moiety or moieties closer to or partlyor wholly within the core of the dendrimer. In another embodiment theHOMO-LUMO energy gap on the dendrite is substantially the same althoughthe surface groups may change the HOMO-LUMO energy gap of thechromophores at the surface of the dendrimer. Sometimes in, say, thesecond generation dendrimer the surface group makes the chromophore atthe distal end of the dendrite of lower HOMO-LUMO energy compared tothat of the next one in.

The relative HOMO-LUMO energy gaps of the moieties can be measured bymethods known per se using a UV-visible spectrophotometer. One of theluminescent moieties may be, or (partly or wholly) within, the coreitself, which will thus preferably have a smaller inherent HOMO-LUMOenergy gap than the other luminescent moiety or moieties in the dendron.Alternatively, or in addition, the dendrons themselves may each containmore than one luminescent moiety, in which case those further from thecore will again preferably have larger inherent HOMO-LUMO energy gapthan those closer to the core. In this case, the core itself need not beluminescent, although luminescent cores are generally preferred.

In a preferred embodiment the dendrimer of the invention is a dendrimerwhich is luminescent in the solid state. In a preferred embodiment thedendrimer of the invention comprises a luminescent core. In a preferredembodiment of the dendrimer of the invention at least one component ofthe dendrons is luminescent.

In a preferred embodiment of the dendrimer of the invention theHOMO-LUMO energy gap of the core is lower than that of the conjugatedmoieties in the dendrons. In a preferred embodiment of the dendrimer ofthe invention the HOMO-LUMO energy gap of the moieties in the dendritegenerally decreases from the surface to the point of attachment to thecore.

The surface groups in a dendrimer of the invention may be the same ordifferent. Likewise, the surface groups within a given dendron of adendrimer of the invention may be the same or different.

Suitable surface groups for the dendrimers include branched andunbranched alkyl (especially t-butyl), branched and unbranched alkoxy,hydroxy, alkylsilane, carboxy, carbalkoxy, and vinyl. A morecomprehensive list includes a further-reactable alkene, (meth)acrylate,sulphur-containing, or silicon-containing group; a sulphonyl group; apolyether group; a C₁-to-C₁₅ alkyl (preferably t-butyl) group; an aminegroup; a mono-, di- or tri-C₁-to-C₁₅ alkyl amine group; a —COOR groupwherein R is hydrogen or C₁-to-C₁₅ alkyl; an —OR group wherein R ishydrogen, aryl, or a C₁-to-C₁₅ alkyl or alkenyl; an —O₂SR group whereinR is C₁-to-C₁₅ alkyl or alkenyl; an —SR group wherein R is aryl, orC₁-to-C₁₅ alkyl or alkenyl; an —SiR₃ group wherein the R groups are thesame or different and are hydrogen, C₁-to-C₁₅ alkyl or alkenyl, or an—SR=group (R=is aryl or C₁-to-C₁₅ alkyl or alkenyl), aryl, orheteroaryl. Typically t-butyl and alkoxy groups are used. Differentsurface groups may be present on different dendrons.

It is preferred that the dendrimer is solution-processable i.e. thesurface groups are such that the dendrimer can be dissolved in asolvent. The surface group can be chosen such that the dendrimer can bephotopatterned. For example, a cross-linkable group is present which canbe cross-linked upon irradiation or by chemical reaction. Alternativelythe surface group comprises a protecting group which can be removed toleave a group which can be cross-linked. In general, the surface groupsare selected so the dendrimers are soluble in solvents suitable forsolution processing.

The aryl (and aryl′) groups within the dendrons can be typicallybenzene, naphthalene, anthracene, fluorene, pyridine, oxadiazole,triazole, triazine, thiophene and where appropriate substitutedvariations. These groups may optionally be substituted, typically by C₁to C₁₅ alkyl or alkoxy groups. The aryl groups at the branching pointsare preferably benzene rings, preferably coupled at ring positions 1, 3and 5, pyridyl or triazinyl rings. The dendrons themselves can containa, or the, fluorescent chromophore.

The cores can be comprised of luminescent or non-luminescent moieties.In the latter case the dendrons must contain luminescent groups. In thecase of the cores being luminescent they can be comprised of eitherorganic and/or organometallic fluorophores and/or phosphors. Typicalcores include one or more moieties of benzene, pyridine, pyrimidine,triazine, thiophene, fluorene, divinylbenzene, distyrylethylene,divinylpyridine, pyrimidine, triazine, divinylthiophene, oxadiazole,coronene, or a fluorescent dye or marker compound or an organometalliccomplex such as a lanthanide, or iridium complex, or a platinumporphyrin, or a distyryl anthracene, porphyrin or distyrylbenzenemoiety. These various rings may be substituted, for example by C₁ to C₁₅alkyl or alkoxy groups.

It is possible to control the electron affinity of the dendrimers by theaddition to the chromophores of electron-withdrawing groups whereappropriate, for example cyano and sulfone which are stronglyelectron-withdrawing and optically transparent in the spectral region weare interested in. Further details of this and other modifications ofthe dendrimers can be found in WO99/21935 to which reference should bemade.

It will be appreciated that one or more of the dendrons attached to thecore (provided that at least one dendron is a specified conjugateddendron) can be unconjugated. Typically such dendrons include ether-typearyl dendrons, for example where benzene rings are attached via amethyleneoxy link.

The dendrimers for the present invention can be prepared in a similarmanner to those described in WO99/21935. In a preferred embodiment, thedendrons are first prepared and then the dendrons are reacted to formthe dendrimer. In the case of Types 1 to 3 this will involve thepreparation of 2 to 3 dendrons whereas in Type 4 only one type ofdendron may need to be prepared. The dendrons are then reacted with afunctionality to form the core.

The dendrimer can be incorporated into a light-emitting device such as alight-emitting diode (LED), also known as an electroluminescent (EL)device, in a conventional manner. In a preferred embodiment thedendrimer acts as the light emitting element. By suitable selection ofdendrons and surface groups the dendrimers can be made soluble inconventional solvents such as toluene, THF, water and alcoholic solventssuch as methanol. In its simplest form, an organic light emitting orelectroluminescent device can be formed from a light emitting layersandwiched between two electrodes, at least one of which must betransparent to the emitted light. Such a device can have a conventionalarrangement comprising a transparent substrate layer, a transparentelectrode layer, a light emitting layer and a back electrode. For thispurpose the standard materials, can be used. Thus, typically, thetransparent substrate layer is made of glass although other transparentmaterials, for example PET, can also be used.

The anode, which is generally transparent, is preferably made fromindium tin oxide (ITO) although other similar materials including indiumoxide/tin oxide, tin oxide/antimony, zinc oxide/aluminum, gold andplatinum can also be used. Conducting polymers such as PANI(polyaniline) or PEDOT (poly(3,4-ethylenedioxythiophene) can also beused.

The cathode is normally made of a low work function metal or alloy suchas Al, Ca, Mg, Li, or MgAg or optionally with an additional layer ofLiF. As is well known, other layers may also be present, including ahole transporting material and/or an electron transporting material. Inan alternative configuration, the substrate may be an opaque materialsuch as silicon and the light is emitted through the opposing electrode.

In a preferred embodiment, the light emitting device of the inventioncomprises a light emitting element comprising a dendrimer according tothe invention. In a preferred embodiment, the light emitting device ofthe invention comprises a layer of a dendrimer according to theinvention together with one or more layers of other materials. In apreferred embodiment, the light emitting device of the inventionincludes a hole-transporting and/or electron-transporting layer. In apreferred embodiment of the light emitting device of the invention, thelayer containing the dendrimer also contains another material,preferably an organic material. In a preferred embodiment, the lightemitting device of the present invention is a light emitting diode(LED).

The dendrimers of the present invention can be deposited by knownsolution processing methods, such as spin-coating, printing ordip-coating. The dendrimer can be deposited as a neat film or as a blendwith dendrimers, polymers and/or molecular materials. The thickness istypically 10 nm to 1000 nm, preferably less than 200 nm, more preferably30-120 nm. Other organic layers, for example charge transportingmaterials, can be deposited on top of the dendrimer film by evaporation,or by solution processing from a solvent in which the first layer is notsoluble.

The dendrimers can also be used in other semiconducting devicesincluding photodiodes, solar cells, FET or a solid state triode.

BRIEF DESCRIPTION OF DRAWINGS FIGURES

FIG. 1 is a schematic diagram of a dendrimer in accordance with theinvention;

FIG. 2 shows the structures of several dendrimers in accordance with theinvention;

FIG. 3 shows a reaction scheme for the preparation of dendrimers inaccordance with the invention;

FIG. 4 shows the absorption and photoluminescence spectra of a blendcomprising dendrimers in accordance with the invention and PBD;

FIG. 5 shows the absorption and photoluminescence spectra of a filmcomprising dendrimers in accordance with the invention and theelectroluminescence emission spectrum of a device including the same;

FIG. 6 shows the current-voltage-luminance characteristics and thecurrent-luminance-efficiency characteristics of a device in accordancewith the invention;

FIG. 7 shows an alternative reaction scheme for the preparation ofdendrimers in accordance with the invention;

FIG. 8 shows the absorption and photoluminescence spectra of a filmcomprising dendrimers in accordance with the invention;

FIG. 9 shows the electroluminescence emission spectrum and thecurrent-voltage-luminance characteristics of a device including a filmcomprising dendrimers in accordance with the invention;

FIG. 10 shows the current-luminance-efficiency characteristics of adevice in accordance with the invention;

FIG. 11 shows the electroluminescence emission spectrum of a device inaccordance with the invention;

FIG. 12 shows the current-voltage-luminance characteristics and thecurrent-luminance-efficiency characteristics of a device in accordancewith the invention;

FIG. 13 shows distyrylbenzene and porphyrin cored dendrimers inaccordance with the invention and the process for making the same; and,

FIG. 14 shows distyrylbenzene cored dendrimers in accordance with theinvention and the process for making the same.

The following Examples further illustrate the present invention.

EXAMPLES

A distyryl benzene dendrimer was prepared comprising dendrons witharyl-vinyl-aryl linkages and with aryl-aryl linkages. The reactionscheme is shown in FIG. 3, and the synthesis detailed in examples 1-2. Adistyryl benzene cored dendrimer was also prepared comprising dendronswith aryl-vinyl-aryl linkages and phenyl-oxadiazole-phenyl linkages. Thereaction scheme for this second compound is shown in FIG. 7, and thesynthesis detailed in examples 3-7.

Example 1 G1-Ar—CHO (1)4-{3′,5′-Di[4″-(2′″-ethylhexyloxy)phenyl]styryl}benzaldehyde

A mixture of the G1-Phosphonate:1-(methylenedimethylphosphonate)-3,5-di[4′-(2″-ethylhexyloxy)phenyl]benzeneof Example 7 of WO 01/59030 (370 mg, 0.607 mmol), (terephthaldehydemono(diethylacetal) (105 mg, 0.507 mmol), potassium tert-butoxide (68mg, 0.606 mmol) and anhydrous THF (15 cm³) was stirred at roomtemperature under argon for 24 h before being cooled. 9 cm³ of 3 MHCl_((aq)) was then added to the mixture and it was stirred at roomtemperature for further 2 h. The aqueous layer was separated andextracted with DCM (2×10 cm³). The DCM extracts and the organic portionwere dried over anhydrous magnesium sulfate, filtered, and the solventswere completely removed to leave a yellow oil. Purification by columnchromatography over silica gel using ethyl acetate-light petroleum (0:1to 1:10) as eluent gave 246 mg (79%) of 1 as a light yellow oil.

Example 2 Asymmetric G1-DSB Core Dendrimer (2)1-[3′,5′-Dis(3″,5″-di-tert-butylstyryl)styryl]-4-{3′″,5′″-di[4″″-(2′″″-ethylhexyloxy)phenyl]styryl}benzene

Potassium tert-butoxide (24 mg, 0.217 mmol) was added to a solution ofthe aldehyde 1 (113 mg, 0.181 mmol), [G-1]phosphonate:1-(methylenedimethylphosphonate)-3,5-bis(3′,5′-di-tert-butylstyryl)benzeneof Example 2A of WO 01/59030 (136 mg, 0.217 mmol) in 6 cm³ of anhydrousTHF at room temperature under argon. After being stirred for 24.5 h, themixture was quenched with 3 cm³ of water. The aqueous layer wasseparated and washed with DCM (2×3 cm³). The combined DCM extracts andthe organic layer were dried over anhydrous magnesium sulfate, filtered,and the solvents were completely removed. The residue was purified bycolumn chromatography over silica gel with ethyl acetate-light petroleum(1:10) as eluent to give 247 mg of a yellowish foam.

The foam and catalytic amount of I₂ were then dissolved in 3 cm³ oftoluene. The solution was heated at reflux for 4 h before being cooled,washed with aqueous sodium metabisulfite solution (10%, 1×5 m³), brine(1×5 cm³) and tried (MgSO₄), and filtered. The solvent was completelyremoved. Purification by column chromatography over silica gel usingethyl acetate-light petroleum (0:1 to 1:10) as eluent gave 241 mg (99%)of 2 as a light yellow/green solid; (Found: C, 88.0; H, 9.2. C₈₂H₁₀₂O₂requires C, 88.0; H, 9.2%); λ_(max)/nm (thin film) 242, 293, 327, 370sh,and 396sh; δ_(H)(400 MHz; CD₂Cl₂) 0.97-1.06 (12 H, m, Me), 1.39-1.67 (52H, m, CH₂ & t-Bu), 1.78-1.92 (2 H, m, CH), 3.94-4.03 (4 H, m, ArOCH₂),7.07-7.74 (32 H, ArH & vinyl H); m/z [MALDI] 1119 (M⁺).

Example 3 Ar—HZ (3)

A mixture of methyl 3,5-di-tert-butylbenzoate (3.88 g, 15.6 mmol),hydrazine hydrate (2.35 g, 46.9 mmol) and MeOH (20 cm³) was heated atreflux overnight. The mixture was allowed to cool and 60 cm³ of waterwas added. The mixture was extracted with ether (3×30 cm³). The etherextracts were combined and washed with NaHCO₃(s,) (1×50 cm³), brine(1×50 cm³), dried (MgSO₄) and filtered. The solvent was completelyremoved to give 3.68 g (94%) of 3 as a white solid; m/z [APCI⁺] 249(MH⁺).

Example 4 Ar—Br (4)

A solution of 3 (2.70 g, 10.9 mmol) in 25 cm³ of anhydrous THF was addedto a mixture of 5-bromo-1,3-benzenedicarbonyl dichloride (1.36 g, 4.83mmol) and anhydrous THF (5 cm³) under argon. The reaction was stirred atroom temperature overnight. The solvent was removed completely. Theresidue was purified by column chromatography over silica gel usingMeOH-DCM (1:99) as eluent and then recrystallised from DCM-MeOH to give4 (2.45 g, 72%); δ_(H)(200 MHz; CDCl₃) 1.30 (36 H, s, t-Bu), 7.56-7.65(6 H, m, ArH), 8.13 (2 H, s, ArH), 8.42 (1H, s, ArH), 9.43 (2 H, br s,CONH), and 10.58 (2 H, br s, CONH); [APCI⁺] 707, and 705 (MH⁺).

Example 5 G1-ODZ-Br (5)3,5-Bis[5′-(3″,5″-di-tert-butylphenyl)-[1′,3′,4′]-oxadiazole-2′-yl]phenylbromide

A mixture of aryl bromide 4 (3.00 g, 4.26 mmol) and phosphorousoxychloride (30 cm³, 9.6 mmol) was heated at reflux under argonovernight. After cooling, the excess phosphorous oxychloride was removedunder reduced pressure. Water (50 cm³) and ether (40 cm³) were added.The two phases were separated. The aqueous layer was extracted withether (2×40 cm³). The organic layer and the ether extracts were combinedand washed with water (1×50 cm³), NaHCO_(3(sat)) (1×50 cm³), dried overanhydrous magnesium sulphate, filtered, and the solvent removed in vacuoto give a white solid. Recrystallisation from DCM-light petroleum gave2.20 g (78%) of 5 as a white crystalline solid; ν_(max)(KBr)/cm⁻¹ 1601(C═N), and 1541 (C═C); ), λ_(max)(CH₂Cl₂)/nm 293 (logε 4.92); δ_(H)(400MHz; CDCl₃) 1.43 (36 H, s, t-Bu), 7.67 (2 H, t, J 2. 0 Hz, ArH), 8.01 (4H, d, J 2.0 Hz, ArH), 8.51(2 H, d, J 1.5 Hz, ArH), and 8.84 (1 H, s,ArH); δ_(C)(100 MHz, CDCl₃) 31.4, 35.1, 121.5, 122.7, 123.5, 123.8,126.5, 126.8, 132.3, 152.0, 162.4, and 166.2; m/z [APCI⁺] 671, and 669(MH⁺).

Example 6 G1-Ar-Sty (6)1-vinyl-4-[3′,5′-di(3″,5″-di-tert-butylstyryl)styryl]benzene

Lithium ethoxide (1.0 M, 5.2 cm³, 5.2 mmol) was added dropwise over 20minutes to a suspension of the3,5-di(3′,5′-di-tert-butylstyryl)benzaldehyde (see WO 99/21935) (1.40 g,2.61 mmol), 4-vinylbenzyltriphenylphosphonium chloride (1.30 g, 3.14mmol) and 15 cm³ of ether. The mixture was stirred at room temperaturefor 1 h and then washed with water (2×30 cm³) and brine (1×30 cm³), anddried (MgSO₄) and filtered. The solvent was completely removed to leavea white solid. The solid was dissolved in DCM and passed through a plugof silica gel using DCM as eluent. The filtrate was collected and thesolvent was completely removed.

The solid and catalytic amount of I₂ were then dissolved in 60 cm³ oftoluene. The mixture was heated at reflux for 2 h before being cooled,washed with aqueous sodium metabisulfite solution (10%, 1×30 m³), brine(1×40 cm³) and dried (MgSO₄) and filtered. The solvent was completelyremoved. Purification by column chromatography over silica gel usingDCM-light petroleum (1:4) as eluent and then recrystallisation fromDCM-MeOH gave 1.19 g (72%) of 6 as a white solid; 8H(²⁰⁰ MHz; CDCl₃)1.39 (36 H, s, t-Bu), 5.28 (1 H, d, J 11.6 Hz, vinyl H), 5.81 (1 H, d, J17.4 Hz, vinyl H), 6.76 (1 H, dd, J 11.6 & 17.4 Hz, vinyl H), 7.12-7.69(19 H, ArH & vinyl H); m/z [APCI⁺] 635 (MH⁺).

Example 7 Asymmetric G1-Oxadiazole DSB Core Dendrimer (7) 1-{3′,5′-Di[5″-(3′″,5′″-di-tert-butylphenyl)-2′-[1″,3″,4″]oxadiazole]styryl}-4-[3″″,5″″-di(3′″″,5′″″-di-tert-butylstyryl)styryl]benzene

A rapidly stirred suspension of 6 (215 mg, 0.340 mmol), 5 (227 mg, 0.340mmol), sodium carbonate (43 mg, 0.410 mmol), 2,6-di-tert-butyl-p-cresol(7.5 mg, 34 mmol), trans-di(μ-aceto)-bis[o-(di-o-tolylphosphino)benzyl]dipalladium (II) (2 mg, 2.0 μmol) and N,N-di-methylacetamide (1.0 cm³)was deoxygenated by alternate exposure to a high vacuum and flushingwith argon for 30 minutes. The solution was heated at 130° C. for 17hours and then was allowed to cool. DCM (50 cm³) and water (50 cm³) wereadded to the mixture and the organic phase was separated, washed withwater (2×20 cm³) and brine (20 cm³), dried over anhydrous magnesiumsulphate, filtered and the solvent removed to give a yellow residue. Theresidue was purified by column chromatography over silica using ethylacetate-DCM (0:1 to 1:19) as eluent to give 214 mg (51%) of 7 as a paleyellow solid; mp>200° C. (decomp.); ν_(max)(KBr)/cm⁻¹ 1595 (C═N), 1544(C═C), and 959 (C═C—H trans); λ_(max)/nm (thin film) 309, and 367;δ_(H)(400 MHz; CDCl₃) 1.41 (36 H, s, t-Bu), 1.46 (36 H, s, t-Bu),7.18-7.35 (14 H, m, vinyl H & ArH), 7.64-7.66 (9 H, m, ArH), 8.06 (4 H,d, J 1.5 Hz, ArH), 8.54 (2 H, d, J 1.0 Hz, ArH), and 8.74 (1 H, t, J 1.0Hz, ArH); m/z [MALDI] 1287 (MCu⁺), and 1224 (MH⁺).

Examples 8 and 9

The dendrimers of Examples 2 and 7 are used as emissive materials inlight-emitting diodes in Examples 8 and 9, respectively. The dendrimers,and dendrimers doped with different concentrations of PBD(2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) or PVK(poly-(9-vinyl)carbazole), were dissolved in tetrahydrofuran (THF)solution at a dendrimer concentration of 10 mg/ml. The devices werefabricated as follows:

-   -   1. ITO treatment: The strip-etched ITO substrates were washed in        an ultrasonic bath of acetone, followed by iso-propanol, and        finally dried before use.    -   2. PEDOT: The PEDOT (poly (2,3-ethylenedioxythiophene Bayer) was        spin-coated onto a treated ITO substrate at a spin speed of 2500        rpm, and baked on a hotplate at 100-150° C. for at least 30 min        before spin-coating the dendrimer layer.    -   3. Single-layer device: The dendrimer, or dendrimer doped with        PBD or PVK, was spin-coated onto the substrate covered by PEDOT        at a spin speed of 1000-1500 rpm, then baked at 50° C. for at        least 30 min to remove solvent from the film. The resulting        films were 80-100 nm thick. The cathode was formed by the        thermal evaporation of Al or MgAl at a pressure of around 3×10⁻⁶        mbar. The thickness of Al or MgAl was approximately 200 nm.

FIG. 5 (top) shows the absorption and PL emission spectra of a film ofcompound 2. FIG. 4 shows the absorption and PL emission of a film of ablend of compound 2 and2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD). FIG. 8shows the absorption and PL emission spectra of a film of compound 7.

The dendrimers of Examples 2 and 7 have been incorporated into singlelayer devices. In the case of the distyrylbenzene dendrimers (example 2)unoptimised devices with structure ITO/PEDOT/dendrimer2/Mg/Al had an ELefficiency of 0.01%, brightness of 65 cd/m², and a power efficiency of0.002 Lm/W. FIG. 5 (bottom) shows the EL emission spectrum of thedevice. FIG. 6 shows the current-voltage-luminance characteristics (top)and the current-luminance-efficiency characteristics (bottom). In thecase of 7 unoptimised devices with structure ITO/PEDOT/dendrimer 7/Mg/Alhad an EL efficiency of 0.002%, brightness of 38 cd/m², and a powerefficiency of 0.0009 Lm/W. FIG. 9 (top) shows the EL spectrum of thedevice ITO/PEDOT/dendrimer 7/MgAl and (bottom) shows thecurrent-voltage-luminance characteristics. FIG. 10 shows thecurrent-luminance-efficiency characteristics of the same device.However, when 7 was used as a blend in PVK (1:0.5) in the same deviceconfiguration the device properties improved so that EL efficiency was0.02% with brightness of 60 cd/m², and a power efficiency of 0.01 Lm/Wsuggesting that 7 was an electron transporter. The EL spectrum,current-voltage-luminance characteristics, andcurrent-luminance-efficiency characteristics of the ITO/PEDOT/PVK:7/MgAl device are shown in FIGS. 11 and 12, respectively.

Example 10

A dendron was synthesised that comprised a mixture ofaryl-acetylenyl-aryl links and aryl-vinyl-aryl links, i.e. that baddifferent links within one dendron, and this was used to form both aporphyrin cored dendrimer (6) and a divinylbenzene cored dendrimer (8).

Distyrylbenzene and porphyrin cored dendrimers containing both alkeneand acetylene links in the dendrons and the process for making them areset out in FIG. 13; the numbers apply accordingly.

1,1-Dibromo-2-{3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethene(2)

Triphenylphosphine (3.92 g, 14.96 mmol) was added in one portion to astirred solution of-3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]benzaldehyde (1) (2.00 g, 3.74mmol) and carbon tetrabromide (2.48 g, 7.38 mmol) in dichloromethane (20mL). Heat was evolved and the mixture stirred at room temperature for 75min. The resultant orange suspension was washed with water (2×50 mL),dried over anhydrous magnesium sulphate, filtered and the solventremoved to leave an orange-brown residue, which was purified by passingthrough a plug of silica with dichloromethane—light petroleum (2:3) aseluent. The solvent was removed to give2-{3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}-1,1-dibromoethene(2) as a white foam (2.45 g, 95%) mp 148-150° C. (Found: C, 69.5; H,7.3; C₄₀H₅₀Br₂ requires C, 69.6; H, 7.3%); ν_(max)(KBr)/cm⁻¹ 1595 (C═C)and 958 (C═C—H trans); λ_(max)(CH₂Cl₂)/nm 306 (log(ε/dm³ mol⁻¹cm⁻¹)4.85), 317 (4.85) and 329sh (4.73); ⁻δ_(H)(400 MHz, CDCl₃) 1.40 (36H, s, t-butyl), 7.14 and 7.24 (4 H, d, J 16, vinyl H) 7.40 (2 H, dd, J1.5, sp H),7.42(4 H, d, J 1.5, sp H), 7.56 (1 H, s, CHCBr₂), 7.60 (2 H,s, cp H) and 7.69 (1 H, s, cp H); m/z (CI+) 692.2 (MH⁺, 100%), 613.2(M−⁷⁹Br, 96%), 611.2 (M−⁸¹Br, 90%) and 533.3 (M−2⁷⁹Br, 74%).

3,5-Bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl acetylene (3)

n-Butyllithium (2.5 M in hexanes, 2.9 mL, 7.20 mmol) was added to asolution of1,1-dibromo-2-{3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethane(2)(2.37 g, 3.43 mmol) in tetrahydrofuran (40 mL) under argon at −78° C.The mixture was stirred at −78° C. for 1 h then at room temperature for1 h. Water (25 mL) was added and the aqueous layer separated andextracted with ether (25 mL). The organic layers were combined, washedwith brine (25 mL), dried over anhydrous magnesium sulphate, filteredand the solvent removed to leave yellow foam. The residue was purifiedby column chromatography over silica with dichloromethane—lightpetroleum (1:3) as eluent. Impure fractions were combined and purifiedby column chromatography with dichloromethane—light petroleum (1:9) aseluent to give 3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl acetylene(3) (1.28 g, 70%) as white solid. mp 156-157° C. (Found: C, 90.6; H,9.5; C₄₀H₅₀ requires C, 90.5; H, 9.5%); ν_(max)(KBr)/cm⁻1595 (C═C) and962 (C═C—H trans); λ_(max)(CH₂Cl₂)/nm 307sh (log(ε/dm³ mol⁻¹ cm⁻¹)4.87), 317 (4.88) and 329sh (4.74); δ_(H)(500 MHz, CDCl₃) 1.39 (36 H, s,t-butyl), 3.11 (1 H, s, CCH), 7.10 and 7.24 (4 H, d, J 16, vinyl H) 7.40(6 H, s, sp H), 7.59 (2 H, s, cp H) and 7.67 (1 H, s, cp H); δ_(C)(125MHz, CDCl₃) 31.4, 34.8, 83.5, 120.86, 122.3, 122.6, 125.0, 125.7, 128.6,130.8, 136.0, 138.0 and 151.0; m/z (EI) 530.4 (M⁺, 100%).

3,5-Bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethynyl)benzaldehyde (4)

Nitrogen was bubbled through a solution of3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl acetylene (3) (1.00 g,1.88 mmol) and 3,5-dibromobenzaldehyde (191 mg, 0.725 mmol) intetrahydrofuran (10 mL) and triethylamine (15 mL) for 15 min.Tetrakis(triphenylphosphine)palladium(0) (60 mg, 52 μmol) and copper(I)iodide (18 mg, 94 μmol) were added and nitrogen bubbled through thesolution for a further 15 min and the mixture then stirred at 70° C. for17.5 h. Once cool, the solvent was removed and the residue purified bycolumn chromatography over silica with dichloromethane—light petroleum(1:2) as eluent to give3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}-ethynyl)benzaldehyde(4) (714 mg, 85%) as a white solid. mp>250° C. (dec.) (Found: C, 89.5;H, 8.5; C₈₇H₁₀₂O requires C, 89.8; H, 8.8%); ν_(max)(KBr)/cm⁻¹ 2215 w(C≡C), 1703 (C═O), 1595 (C═C) and 957 (C═C—H trans): λ_(max)(CH₂Cl₂)/nm318 (log(ε/dm³ mol⁻¹ cm⁻¹) 5.12) and 330sh (4.93); δ_(H)(400 MHz, CDCl₃)1.41 (72 H, s, t-butyl), 7.15 and 7.30 (8 H, d, J 16.5, vinylic H), 7.42(4 H, dd, J 1.5, H), 7.44 (8 H, d, J 1.5, sp H), 7.69 (4 H, d, J 1, bpH), 7.71 (2 H, s, bp H), 8.02 (1 H, dd, J 1.5, cp H), 8.06 (2 H, d, J1.5, cp H) and 10.01 (1 H, s, CHO); δ_(c)(100.6 MHz, CDCl₃) 31.5, 34.9,87.1, 91.6, 121.0, 122.5, 123.1, 124.9, 125.3, 126.8, 128.3, 131.0,132.0, 136.1, 136.7, 138.3, 139.6, 151.1 and 191.0; m/z (MALDI) 1163.1(M⁺, 100%).

5,10,15,20-Tetrakis [(3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethynyl)-phenyl]porphyrin (6)

A solution of trifluoroacetic acid (6.6 μL, 0.086 mmol) indichloromethane (1.32 mL) was added to a stirred solution of3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}-ethynyl)benzaldehyde(4) (100.0 mg, 0.086 mmol) and pyrrole (5) (6.0 μL, 0.086 mmol) indichloromethane (2.5 mL) and the mixture stirred in the dark under argonfor 12 days 18 h. 2,3-Dichloro-5,6-dicyanobenzoquinone (19.6 mg, 0.086mmol) was added and the mixture stirred for 30 min then neutralised bythe addition of an excess of sodium bicarbonate and filtered through aplug of silica, eluting with dichloromethane until the filtrate wascolourless. The solvent was removed and the residue purified by columnchromatography over silica with dichloromethane—light petroleum (1.4) aseluent to give5,10,15,20-tetrakis[(3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethynyl)-phenyl]porphyrin(6) (38.5 mg, 37%) as a red-brown solid. δ_(H)(400 MHz, CDCl₃)−2.70 (2H, s, NH), 1.31 (288 H, s, t-butyl H), 7.08 and 7.23 (32 H, d, J 16,vinyl H), 7.32 (16 H, dd, J 1.5, sp-H), 7.35 (32 H, d, J 1.5, sp-H),7.65 (8 H, s, bp-H), 7.69 (16 H, s, bp-H), 8.27 (4 H, s, cp-H), 8.45 (8H, d, J 1, cp-H) and 9.08 (8 H, s, β-pyrrolic H); m/z (MALDI) 4844.2(M⁺, 100%).

1,4-Bis{[2-(3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethynyl)vinyl]-phenyl}benzene(8)

Tetrahydrofuran (15 mL) was added to a flask containing3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}-ethynyl)benzaldehyde(4) (500 mg, 4.30 mmol), [4-(dimethoxyphosphorylmethyl)benzylphosphonicacid dimethyl ester (7) (65.9 mg, 2.05 mmol) and potassium tert-butoxide(57.4 mg, 5.11 mmol). The solution immediately turned red and wasstirred under nitrogen for 67 h. Water (20 mL) was added and theemulsion extracted with dichloromethane (4×50 mL). The organic layerswere combined, washed with brine (50 mL), dried over anhydrous magnesiumsulphate, filtered and the solvent removed. Column chromatography of theresidue over silica with dichloromethane—light petroleum (1:4 to 1:2)gave a yellow solid that was a mixture of isomers. The solid was heatedwith iodine (90 mg, 0.35 mmol) in toluene (20 mL) at 90° C. for 45 h.The solution was allowed to cool and washed with saturated aqueoussodium metabisulphite solution (20 mL) and brine (20 mL) and the solventremoved. The residue was passed through a plug of silica andrecrystallised from a dichloromethane—hexanes mixture to leave a yellowsolid1,4-Bis{[2-(3,5-bis({3,5-bis[2-(3,5-di-tert-butylphenyl)vinyl]phenyl}ethynyl)vinyl]-phenyl}benzene(8) (314 mg, 64%). δ_(H)(200 MHz, CDCl₃) 1.41 (144 H, s, t-butyl),7.20-7.36 (20 H, m, vinyl H), 7.42-7.45 (24 H, m, surface phenyl H) and7.62-7.75 (22 H, m, phenyl H).

Example 11

Distyrylbenzene cored dendrimers containing alkene and acetylene linkeddendrons and alkene linked and ether linked dendrons and the process formaking them are set out in FIG. 14; the numbers apply accordingly.

4-(2-Ethylhexyloxy)iodobenzene (2)

A suspension of potassium hydroxide (11.0 g, 196 mmol) in dimethylsulphoxide (70 mL) was degassed under high vacuum for 10 minutes.4-Iodophenol (1) (10.0 g, 45.5 mmol) and 2-ethylhexyl bromide (16.2 mL,90.9 mmol) were added and the solution stirred at room temperature underargon for 65 h. The resultant suspension was poured into ice-water (150mL) and the slurry extracted with light petroleum (2×100 mL). Theorganic extracts were combined, washed with brine (100 mL), dried overanhydrous magnesium sulphate, filtered and the solvent removed. Theresidue was purified by column chromatography over silica with lightpetroleum as eluent to give 4-(2-ethylhexyloxy)iodobenzene (2) (14.2 g,94%) as a clear, colourless oil which had the same ¹H and ¹³C nmrspectra as reported in the literature. [see A. R. A. Palmans, M. Elginand A. Montalli, Chem. Mater., 2000, 12 (2), 472-480]

[4-(2-Ethylhexyloxy)phenylethynyl]trimethylsilane (3)

Tetrakis(triphenylphosphine)palladium(0) (0.52 g, 0.45 mmol) was addedto a degassed suspension of trimethylsilyl acetylene (3.00 mL, 2.09 g,21.2 mmol), 4-(2-ethylhexyloxy)iodobenzene (2) (4.27 g, 12.9mmol) andcopper (I) iodide (294 mg, 1.54 mmol) in tetrahydrofuran (20 mL) andtriethylamine (30 mL). The mixture was stirred under argon at roomtemperature for 64.5 h. The solution was filtered through a short plugof silica with dichloromethane as eluent and the solvent removed. Theresidue was purified by column chromatography over silica with lightpetroleum as eluent to leave[4-(2-ethylhexyloxy)phenylethynyl]trimethylsilane (3) (2.93 mg, 75%) asa clear, colourless oil. (Found: C, 75.35; H, 9.85. Cl₉H₃₀OSi requiresC, 75.43; H, 10.0%); ν-_(max)(film)/cm⁻2156 (C≡C); δ_(H)(400 MHz, CDCl₃)0.25 (9 H, s, SiMe₃), 0.92 (6 H, m, CH₃), 1.30-1.51 (8 H, m,CHCH₂CH₂CH₂CH₃ and CHCH₂CH₃) 1.72 (1 H, OCH₂CR), 3.84 (2 H, d, J5,OCH₂CH) and 6.82 and 7.40 (4 H, AA′BB′, phenyl H); δ_(c)(100.6 MHz,CDCl₃) 0.1, 11.1, 14.1, 23.0, 23.8, 29.0, 30.4, 39.3, 70.5, 92.2, 105.3,114.3, 114.8, 133.4 and 159.6.

1-(2-Ethylhexyloxy)-4-ethynylbenzene (4)

Tetrabutylammonium fluoride (1.0 M in tetrahydrofuran, 13.2 mL, 13.2mmol) was added to a stirred solution of[4-(2-ethylhexyloxy)phenylethynyl]trimethylsilane (3) (2.59 g, 13.2mmol) in tetrahydrofuran (70 mL) and the solution stirred under nitrogenat room temperature for 100 min. The solvent was removed and the residuepassed through a plug of silica with dichloromethane—light petroleum(1:9) as eluent to give 1-(2-ethylhexyloxy)-4-ethynylbenzene (4) (1.96g, 99%) as a pale yellow-brown oil. (Found: C, 83.4, H, 9.85, C₁₉H₃₀OSirequires C, 83.4; H, 9.6%); ν_(max)(film)/cm⁻¹ 3294 and 3317 (C≡C—H) and2107 (C≡C); δ_(H)(400 MHz, CDCl₃) 0.94 (6 H, m, CH₃), 1.28-1.57 (8 H, m,CHCH₂CH₂CH₂CH₃ and CHCH₂CH₃), 1.74 (1H, m, OCH₂CH), 3.01 (1 H, s, CCH),3.85 (2 H, d, J 5, OCH₂CH), and 6.85 and 7.43 (4 H, AA′BB′, phenyl H);δ_(c)(100.6 MHz, CDCl₃) 11.1, 14.1, 23.0, 23.8, 29.0, 30.4, 39.3, 70.5,75.6, 83.8, 113.7, 114.4, 133.5, 159.8.

3,5-Bis[4-(2-ethylhexyloxy)phenylethynyl]benzaldehyde (6)

Nitrogen was bubbled through a solution of1-(2-Ethylhexyloxy)-4-ethynylbenzene (4) (1.69 g, 7.34 mmol) and3,5-dibromobenzaldehyde (5) (692 mg, 2.62 mmol) in tetrahydrofuran (33mL) and triethylamine (50 mL) for 5 min.Tetrakis(triphenylphosphine)palladium(0) (218 mg, 0.189 mmol) andcopper(I) iodide (65 mg, 0.34 mmol) were added and nitrogen bubbledthrough the solution for a further 5 min, before stirring at 70° C. for23 h. Once cool, the solvent was removed and the residue purified bycolumn chromatography over silica with dichloromethane—light petroleum(1:2 to 1:1) as eluent to leave3,5-bis[4-(2-ethylhexyloxy)phenylethynyl]benzaldehyde (6) (1.17 g, 79%)as a pale brown oil. (Found: C, 83.3, H, 8.2, C₃₉H₄₆O₃ requires C, 83.2;H, 8.2%); ν_(max)(film)/cm⁻¹ 2211 (C≡C) and 1704 (C═O); δ_(H)(400 MHz,CDCl₃) 0.93-0.99 (12 H, m, CH₃), 1.28-1.56 (16 H, m, CHCH₂CH₂CH₂CH₃ andCHCH₂CH₃), 1.75 (2 H, m, OCH₂CH), 3.87 (4 H, d, J 6 OCH₂CH), 6.90 (4 H,AA′BB′), 7.48 (4 H, AA′BB′), 7.87 (1 H, dd, J 1.5, 4-H), 7.92 (2, H, d,J 1.5, 2, 6-H) and 10.00 (1 H, s, CHO); δ_(c)(100.6 MHz, CDCl₃) 11.1,14.1, 23.1, 23.8, 29.0, 30.4, 39.3, 70.6, 86.0, 91.7, 114.1, 114.6,125.2, 131.3, 133.5, 136.6, 139.1, 159.9 and 191.0.

4-Methylbenzylphosphonium chloride (8)

A solution of triphenylphosphine (25.24 g, 96.22 mmol) and4-methylbenzyl chloride (7) (15.0 g, 0.107 mol) in toluene (100 mL) wasstirred at 110° C. for 28 h and allowed to cool. The resultantprecipitate was collected, washed with toluene and hexane then driedunder vacuum to leave 4-methylbenzylphosphonium chloride (8) (27.64 g,64%) as a white solid. δ_(H)(200 MHz, CDCl₃) 2.20 (3 H, d, CH₃), 5.30 (2H, d, CH₂P), 6.89 (4 H, AA′BB′) and 7.53-7.80 (15 H, m, Ph).

4-({3,5-Bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)toluene (9)

Lithium ethoxide (1.0 M in ethanol, 15.0.mL, 15 mmol) was added to astirred suspension of3,5-bis[(3,5-di-tert-butylphenyl)vinyl]benzaldehyde (A) (WO99/9921935)(4.00 g, 7.48 mmol) and 4-methylbenzylphosphoniumchloride (8) (3.62 g,8.98 mmol) in diethyl ether (40 mL), giving a clear orange solutionwhich was stirred at room temperature for 2 h. The solution was washedwith water (3×40 mL) and brine (40 mL), dried over anhydrous magnesiumsulphate, filtered and the solvent removed, This residue was passedthrough a plug of silica with dichloromethane—light petroleum (1:4) aseluent to give a white solid, which was found by ¹H NMR to be mainly cisisomer. The solid was heated with iodine (210 mg) and toluene (100 mL)at 100° C. under argon for 6 h and allowed to cool. The solution waswashed with saturated aqueous sodium metabisulphite (50 mL) and brine(50 mL) and the solvent removed. The residue was recrystallised from adichloromethane—hexanes mixture to leave4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)toluene (9)(3.00 g, 64%) as a white solid. δ_(H)(400 MHz, CDCl₃) 1.40 (36 H, s,t-butyl), 2.39 (3 H, s, CH₃), 7.13 and 7.22 (2 H, d, J 16, core vinylH), 7.17 and 7.28 (4 H, d, J 16, branch vinyl H), 7.21 and 7.48 (4 H,AA′BB′, core phenyl H), 7.39 (2 H, dd, J 1.5, sp H), 7.43 (4 H, d, J1.5, sp H), 7.59 (2 H, d, J 1, bp H) and 7.62 (1 H s, bp H).

4-({3,5-Bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)benzylphosphonicacid dimethyl ester (10)

A mixture of4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)toluene (9)(2.06 g, 3.30 mmol), N-bromosuccinimide (0.587 g, 3.30 mmol), AIBN (10mg, 0.61 mmol) and chloroform (10 ml) was heated to reflux for 3.5 h andallowed to cool. The suspension was filtered through a plug of silicawith dichloromethane as eluent and the solvent removed to leave a whitesolid which was a mixture of unreacted4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}-vinyl)toluene (9) and4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]-phenyl}vinyl)benzyl bromide.Trimethylphosophite (13.0 mL, 0.110 mol) was added and the solutionheated to 110° C. for 18 h. Excess trimethylphosphite was removed bydistillation under reduced pressure. The residue was purified by columnchromatography over silica with dichloromthane-ethyl acetate (1:0 to0:1) as eluent, then recrystallisation from a dichloromethane—methanolmixture gave4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)benzylphosphonicacid dimethyl ester (10) (723 mg, 30%) as a white solid. δ_(H)(400 MHz,CDCl₃) 1.39 (36 H, s, t-butyl), 3.21 (2 H, d, J 22, CH₂P), 3.71 (6 H, d,J 11, OCH₃), 7.155 and 7.21 (2 H, d, J 16, core vinyl H), 7.164 and 7.27(4 H, d, J 16, branch vinyl H), 7.33 (2 H, m, AA′BB′, core phenyl H),7.39 (2 H, dd, J 1.5, sp H), 7.43 (4 H, d, J 1.5, sp H), 7.53 (2 H, m,AA′BB′, core phenyl H), 7.58 (2 H, d, J 1.5, bp H), and 7.63 (1 H, s, bpH); m/z (APCI+) 730.9 (MH⁺, 100%).

1-{[3,5-bis(benzyloxy)phenyl]vinyl}-4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}-vinyl)benzene (11)

A solution of 3,5-bis(benzyloxy)benzaldehyde (B) (87.1 mg, 2.74 mmol),4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)benzylphosphonicacid dimethyl ester (10) (200 mg, 2.74 mmol) and potassium tert-butoxide(36.8 mg, 3.28 mmol) in tetrahydrofuran (4 mL) was stirred at roomtemperature in the dark for 20.75 h. The solution turned red-orange andacquired blue fluorescence. Ether (20 mL) was added and the solutionwashed with water (20 mL) and brine (20 mL), dried over anhydrousmagnesium sulphate, filtered and the solvent removed. The residue waspurified by column chromatography over silica with dichloromethane—lightpetroleum as eluent to leave1-{[3,5-bis(benzyloxy)phenyl]vinyl}-4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}-vinyl)benzene(11) (194 mg, 77%) as a beige solid. δ_(H)(400 MHz, CDCl₃) 1.42 (36 H,s, t-butyl), 6.60 (1 H, dd, J 2, phenoxy bp-H), 6.83 (2 H, d, J 2,phenoxy bp-H), 7.10 (2 H, s, core vinyl H), 7.18-7.34 (6 H, m, vinylicH), 7.34-7.66 (23 H, m, phenyl H).

1-({3,5-Bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)-4-[(3,5-bis{[4-(2-ethylhexyloxy)phenyl]ethynyl}phenyl)vinyl]benzene(12)

Potassium tert-butoxide (36.8 mg, 3.28 mmol) was added to a solution of3,5-bis[4-(2-ethylhexyloxy)phenylethynyl]benzaldehyde (6) (153 mg, 2.74mmol) and4-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)benzylphosphonicacid dimethyl ester (10) (200 mg, 2.74 mmol) in tetrahydrofuran (4 mL)and the mixture stirred at room temperature in the dark for 19 h. Thesolution turned red-orange and acquired blue fluorescence. Ether (20 mL)was added and the solution washed with water (5 mL) and brine (5 mL),dried over anhydrous magnesium sulphate, filtered and the solventremoved. The residue was purified by column chromatography over silicawith dichloromethane—light petroleum as eluent to leave1-({3,5-bis[(3,5-di-tert-butylphenyl)vinyl]phenyl}vinyl)-4-[(3,5-bis{[4-(2-ethylhexyloxy)-phenyl]ethynyl}phenyl)vinyl]benzene(12) (241 mg, 76%) as a yellow solid. δ_(H)(400 MHz, CDCl₃) 0.95 (12 H,m, CH₃), 1.41-1.60 (16 H, m, CHCH₂CH₂CH₂CH₃ and CHCH₂CH₃), 1.42 (36 H,s, t-butyl), 1.78 (2 H, m, OCH₂CR), 3.89 (4 H, d, J 6, OCH₂CH), 6.93 (4H, AA′BB′, phenoxy sp-H), 7.12-7.34 (8 H, m, vinylic H), 7.43 (2 H, dd,J 1.5, sp-H), 7.48 (4 H, d, J 1.5, sp-H) and 7.51 - 7.67 (10 H, m, DSBphenyl H).

Example 12

Devices of the structure (ITO/PEDOT/dendrimer/LiF/Ca/Al) were preparedby the following general procedure:

-   1. Etch ITO squares 12×12 mm into 4×12 mm ITO strip by acid etch.-   2. Acetone rinse for 10 minutes with ultrasonication.-   3. Propan-2-ol rinse for 10 minutes with ultrasonication.-   4. Substrates dry under nitrogen flow.-   5. Substrates subject to oxygen plasma treatment for 5 minutes at    100 W.-   6. PEDOT spun from water solution at 2500 rpm for 1 minute.-   7. PEDOT layer dried in air at 85° C. for 5 minutes.-   8. Dendrimer film deposited by spin coating from tetrahydrofuran at    2000 rpm giving film thicknesses of around 80-90 nm.-   9. Substrates placed in vacuum evaporator.-   10. LiF followed by Ca followed by Al deposited under vacuum.    The following device results were obtained:    Compound 8 of Example 10:

CIE co-ordinates (0.22, 0.29); external quantum efficiency=0.18 at 10V.

Compound 11 of Example 11:

CIE co-ordinates (0.38, 0.47); external quantum efficiency=0.06 at 30V.

Compound 12 of Example 11:

CIE co-ordinates (0.30; 0.35); external quantum efficiency=0.02 at 15V.

1. A light emitting dendrimer having the formula:CORE−[DENDRITE¹]_(n)[DENDRITE²]_(m) in which CORE represents an atom orgroup, n and m, which may be the same or different, each represent aninteger of at least 1, each DENDRITE¹, which may be the same ordifferent when n is greater than 1, and each DENDRITE², which may be thesame or different when m is greater than 1, represent dendriticstructures, at least one of said structures being fully conjugated andcomprising aryl and/or heteroaryl groups and, optionally, vinyl and/oracetylenyl groups, connected via sp² or sp hybridized carbon atoms ofsaid aryl, heteroaryl, vinyl and acetylenyl groups, and at least onebranching point and/or link between the branching points in DENDRITE¹being different from those in DENDRITE², CORE terminating in the singlebond which is connected to a sp² hybridized (ring) carbon atom of thefirst (hetero)aryl group to which more than one conjugated dendriticbranch is attached, said ring carbon atom forming part of said fullyconjugated DENDRITE¹ or DENDRITE² and CORE terminating at the singlebond to the first branching point for the other of said DENDRITE¹ orDENDRITE², at least one of the CORE, DENDRITE¹ and DENDRITE² beingluminescent.
 2. A dendrimer according to claim 1 wherein at least one ofDENDRITE¹ and DENDRITE² comprisesaryl-(vinyl)_(x)-[(aryl′)-(vinyl)_(y)]_(z)-aryl;or aryl-(acetylenyl)_(x)-[(aryl′)-(acetenyl)_(y)]_(z), -aryl;or aryl- (vinyl)_(x)-(aryl′)_(z)-(acetylenyl)_(y)-aryl links where x, yand z, which can be the same or different, are integers from 0 to 3, theorder of the vinyl, aryl′ and acetylenyl groups can be varied, arylincludes heteroaryl and aryl′ is the same as or different from aryl andsaid aryl groups are branching points.
 3. A dendrimer according to claim2, wherein at least one of DENDRITE¹ and DENDRITE² comprisesaryl-(aryl′)_(a)-aryl links and the other comprisesaryl-(vinyl)_(x)-[(aryl′)_(v)-(vinyl)_(y)]_(z)-aryl links where x is aninteger from 1 to 3 and a, y, v and z, which can be the same ordifferent, are integers from 0 to 3, and said aryl groups are branchingpoints.
 4. A dendrimer according to claim 2, wherein at least one ofDENDRITE¹ and DENDRITE² comprises aryl-(aryl′)_(a)-aryl links where a isan integer from 0 to 3 and the other one of DENDRITE¹ and DENDRITE²comprises aryl-(acetylenyl)_(d)-[(aryl′)_(e)-(acetylenyl)_(f)]_(g)-aryllinks where d is an integer from 1 to 3, f is an integer from 0 to 3,and e and g, which can be the same or different, are integers from 0 to3, and said aryl groups are branching points.
 5. A dendrimer accordingto claim 2, wherein one of DENDRITE¹ and DENDRITE² comprisesaryl-(vinyl)_(x)-[(aryl′)_(v)-(vinyl)_(y)]_(z)-aryl links and the otherof DENDRITE¹ and DENDRITE² comprisesaryl-(acetylenyl)_(d)-[(aryl′)_(e)-(acetylenyl)_(f)]_(g)-aryl linkswhere d and x, which can be the same or different, are integers from 1to 3, y and f, which can be the same or different, are integers from 0to 3, and v, e, z and g, which can be the same or different, areintegers from 0 to 3, and said aryl groups are branching points.
 6. Adendrimer according to claim 3, wherein in at least one of DENDRITE¹ andDENDRITE² the links between adjacent branching points are not all thesame.
 7. A dendrimer according to claim 1, wherein DENDRITE¹ andDENDRITE² both represent said fully conjugated structures.
 8. Adendrimer according to claim 1, wherein if DENDRITE¹ differs fromDENDRITE² merely in a different link then, for two links to be regardedas different one said link must comprise at least one aryl, heteroaryl,vinyl or acetylenyl group which is not present in the other of said twolinks.
 9. A dendrimer according to claim 4, wherein in at least one ofDENDRITE¹ and DENDRITE² the links between adjacent branching points arenot all the same.
 10. A dendrimer according to claim 5, wherein in atleast one of DENDRITE¹ and DENDRITE² the links between adjacentbranching points are not all the same.
 11. A dendrimer according toclaim 5, wherein x and d are 1 and z and g are
 0. 12. A dendrimeraccording claim 1, wherein at least one of DENDRITE¹ and DENDRITE²comprises one or more (hetero)aryl linking groups.
 13. A dendrimeraccording to claim 1 wherein at least one of DENDRITE¹ and DENDRITE²does not have an inherently at least partly conjugated molecularstructure.
 14. A dendrimer according to claim 1 wherein the COREcomprises at least one moiety selected from the group consisting ofbenzene, pyridine, pyrimidine, triazine, thiophene, fluorene,divinylbenzene, distyrylethylene, divinylpyridine, pyrimidine, triazine,divinylthiophene, oxadiazole, coronene, fluorescent dye compounds,fluorescent marker compounds, organometallic complexes, distyrylanthracene moieties, porphyrin moieties, and distyrylbenzene moieties.15. A dendrimer according to claim 1 wherein the aryl groups areselected from the group consisting of benzene, pyridine and triazine.16. A dendrimer according to claim 1, wherein the dendrimer comprises atleast one surface group attached to a distal (hetero)aryl ring carbon ofsaid conjugated dendrite.
 17. A dendrimer according to claim 1, whereinat least one surface group is selected from further-reactable alkenes,(meth)acrylates, sulphur-containing groups, silicon-containing groups;sulphonyl groups; polyether groups; C₁-to-C₁₅ alkyl groups; aminegroups; mono-C₁-to-C₁₅ alkyl amine groups, di-C₁-to-C₁₅ alkyl aminegroups, tri-C₁-to-C₁₅ alkyl amine groups; —COOR groups wherein R ishydrogen or C₁ to C₁₅ alkyl; —OR groups wherein R is hydrogen, aryl,C₁-to C₁₅ alkyl or C₁-to C₁₅ alkenyl; —O₂SR groups wherein R isC₁-to-C₁₅ alkyl or C₁-to C₁₅ alkenyl; —SR groups wherein R is aryl, C₁to C₁₅ alkyl or C₁-to C₁₅ alkenyl; —SiR₃ groups wherein the R groups arethe same or different and are hydrogen, C₁ to C₁₅ alkyl or C₁-to C₁₅alkenyl, —SR=groups where R=is aryl, C₁-to-C₁₅ alkyl or C₁-to-C₁₅alkenyl, aryl, and heteroaryl.
 18. A dendrimer according to claim 1wherein the surface group is such as to allow processing followed byphotopatterning.
 19. A light-emitting device which comprises a dendrimeras claimed in claim
 1. 20. A light emitting device in which a lightemitting element is a dendrimer as claimed in claim
 1. 21. A lightemitting dendrimer having the formula:CORE−[DENDRITE]_(n) in which CORE represents an atom or group, nrepresents an integer of at least 1, each DENDRITE, which may be thesame or different, represents an inherently at least partiallyconjugated dendritic molecular structure which comprises aryl and/orheteroaryl and, optionally, vinyl and/or acetylenyl groups, connectedvia sp² or sp hybridized carbon atoms of said aryl, heteroaryl, vinyland acetylenyl groups, and wherein the links between at least one pairof adjacent branching points in said DENDRITE are different such that iftwo links are to be regarded as different then one said link mustcomprise at least one aryl, heteroaryl, vinyl or acetylenyl group whichis not present in the other of said two links, CORE terminating in thesingle bond which is connected to a sp² hybridized (ring) carbon atom ofthe first (hetero)aryl group to which more than one dendritic branch isattached, said ring carbon atom forming part of said DENDRITE, at leastone of the CORE and the DENDRITE being luminescent.
 22. A dendrimeraccording to claim 21, wherein the different types of links are selectedfrom aryl-(aryl)_(a)-aryl,aryl-(vinyl)_(x)-[(aryl′)_(v)-(vinyl)_(y)]_(z)-aryl, and aryl(acetylenyl)_(d)-[(aryl′)_(e)-(acetylenyl)_(f)]_(g)-aryl, where x and d,which can be the same or different, are integers from 1 to 3, y and f,which can be the same or different, are integers from 0 to 3, and a, g,z, e and v, which can be the same or different, are integers from 0 to3, said aryl groups being branching points.
 23. A dendrimer according toclaim 22, wherein a is 0 or 1, x and d are 1, and z and g are
 0. 24. Adendrimer according to claim 21, wherein DENDRITE comprises one or more(hetero)aryl linking groups.
 25. A dendrimer according to claim 21 whichcomprises at least one DENDRITE, which does not have an inherently atleast partly conjugated molecular structure.
 26. A dendrimer accordingto claim 21 wherein the CORE comprises at least one moiety selected fromthe group consisting of benzene, pyridine, pyrimidine, triazine,thiophene, fluorene, divinylbenzene, distyrylethylene, divinylpyridine,pyrimidine, triazine, divinylthiophene, oxadiazole, coronene,fluorescent dye compounds, fluorescent marker compounds, organometalliccomplexes, distyryl anthracene moieties, porphyrin moieties, anddistyrylbenzene moieties.
 27. A dendrimer according to claim 21 whereinthe aryl groups are selected from the group consisting of benzene,pyridine and triazine.
 28. A dendrimer according to claim 21, whereinthe dendrimer comprises at least one surface group attached to a distal(hetero)aryl ring carbon of said conjugated dendrite.
 29. A dendrimeraccording to claim 28, wherein at least one surface group is selectedfrom further-reactable alkenes, (meth)acrylates, sulphur-containinggroups, silicon-containing groups; sulphonyl groups; polyether groups;C₁-to-C₁₅ alkyl groups; amine groups; mono-C₁-to-C₁₅ alkyl amine groups,di-C₁-to-C₁₅ alkyl amine groups, tri-C₁-to-C₁₅ alkyl amine groups; —COORgroups wherein R is hydrogen or C₁ to C₁₅ alkyl; —OR groups wherein R ishydrogen, aryl, C₁-to C₁₅ alkyl or C₁-to C₁₅ alkenyl; —O₂SR groupswherein R is C₁-to-C₁₅ alkyl or C₁-to C₁₅ alkenyl; —SR groups wherein Ris aryl, C₁ to C₁₅ alkyl or C₁-to C₁₅ alkenyl; —SiR₃ groups wherein theR groups are the same or different and are hydrogen, C₁ to C₁₅ alkyl orC₁-to C₁₅ alkenyl, —SR=groups where R=is aryl, C₁-to-C₁₅ alkyl orC₁-to-C₁₅ alkenyl, aryl, and heteroaryl.
 30. A dendrimer according toclaim 29 wherein the surface group is such as to allow processingfollowed by photopatterning.
 31. A light-emitting device which comprisesa dendrimer as claimed in claim
 21. 32. A light emitting device in whicha light emitting element is a dendrimer as claimed in claim 21.